Late mortality due to infection in severe burns has not improved in twenty years. Neutropenia and anemia are common findings in infected burn patients and experimental animals. In this setting suppression of hematopoiesis has been demonstrated, and, recently, a serum inhibitor of in vitro erythropoiesis has been reported. We hope to better define hematological abnormalities following thermal burns by measuring serum erythropoietin and colony stimulating activity, assaying serum for hematopoietic inhibitors, and determing the net effect these regulators have on granulocytic and erythroid differentiation. After informed consent, patients with greater than 30 percent thermal burns who are admitted to the burn unit will be studied. Serum samples will be collected for thirty days. At least two bone marrow aspirates will be obtained for erythroid and granulocytic cultures. A second group of burn patients will be randomly selected to receive transfusions sufficient to maintain the hematocrit between 40-50 percent. All data described above will be collected on this group of patients to determine if granulopoiesis can be augmented by suppressing erythropoiesis.